Subthreshold Nanosecond Laser Intervention in Age-Related Macular Degeneration: The LEAD Randomized Controlled Clinical Trial.

PURPOSE: There is an urgent need for a more effective intervention to slow or prevent progression of age-related macular degeneration (AMD) from its early stages to vision-threatening late complications. Subthreshold nanosecond laser (SNL) treatment has shown promise in preclinical studies and a pilot study in intermediate AMD (iAMD) as a potential treatment. We aimed to evaluate the safety of SNL treatment in iAMD and its efficacy for slowing progression to late AMD. DESIGN: The Laser Intervention in Early Stages of Age-Related Macular Degeneration (LEAD) study is a 36-month, multicenter, randomized, sham-controlled trial. PARTICIPANTS: Two hundred ninety-two participants with bilateral large drusen and without OCT signs of atrophy. METHODS: Participants were assigned randomly to receive Retinal Rejuvenation Therapy (2RT®; Ellex Pty Ltd, Adelaide, Australia) SNL or sham treatment to the study eye at 6-monthly intervals. MAIN OUTCOME MEASURES: The primary efficacy outcome was the time to development of late AMD defined by multimodal imaging (MMI). Safety was assessed by adverse events. RESULTS: Overall, progression to late AMD was not slowed significantly with SNL treatment compared with sham treatment (adjusted hazard ratio [HR], 0.61; 95% confidence interval [CI], 0.33-1.14; P = 0.122). However, a post hoc analysis showed evidence of effect modification based on the coexistence of reticular pseudodrusen (RPD; adjusted interaction P = 0.002), where progression was slowed for the 222 participants (76.0%) without coexistent RPD at baseline (adjusted HR, 0.23; 95% CI, 0.09-0.59; P = 0.002), whereas an increased progression rate (adjusted HR, 2.56; 95% CI, 0.80-8.18; P = 0.112) was observed for the 70 participants (24.0%) with RPD with SNL treatment. Differences between the groups in serious adverse events were not significant. CONCLUSIONS: In participants with iAMD without MMI-detected signs of late AMD, no significant difference in the overall progression rate to late AMD between those receiving SNL and sham treatment were observed. However, SNL treatment may have a role in slowing progression for those without coexistent RPD and may be inappropriate in those with RPD, warranting caution when considering treatment in clinical phenotypes with RPD. Our findings provide compelling evidence for further trials of the 2RT® laser, but they should not be extrapolated to other short-pulse lasers.

Estimating Phosphene Locations Using Eye Movements of Suprachoroidal Retinal Prosthesis Users.

Purpose: Accurate mapping of phosphene locations from visual prostheses is vital to encode spatial information. This process may involve the subject pointing to evoked phosphene locations with their finger. Here, we demonstrate phosphene mapping for a retinal implant using eye movements and compare it with retinotopic electrode positions and previous results using conventional finger-based mapping. Methods: Three suprachoroidal retinal implant recipients (NCT03406416) indicated the spatial position of phosphenes. Electrodes were stimulated individually, and the subjects moved their finger (finger based) or their eyes (gaze based) to the perceived phosphene location. The distortion of the measured phosphene locations from the expected locations (retinotopic electrode locations) was characterized with Procrustes analysis. Results: The finger-based phosphene locations were compressed spatially relative to the expected locations all three subjects, but preserved the general retinotopic arrangement (scale factors ranged from 0.37 to 0.83). In two subjects, the gaze-based phosphene locations were similar to the expected locations (scale factors of 0.72 and 0.99). For the third subject, there was no apparent relationship between gaze-based phosphene locations and electrode locations (scale factor of 0.07). Conclusions: Gaze-based phosphene mapping was achievable in two of three tested retinal prosthesis subjects and their derived phosphene maps correlated well with the retinotopic electrode layout. A third subject could not produce a coherent gaze-based phosphene map, but this may have revealed that their phosphenes were indistinct spatially. Translational Relevance: Gaze-based phosphene mapping is a viable alternative to conventional finger-based mapping, but may not be suitable for all subjects.

The Short-Term Compliance and Concordance to in Clinic Testing for Tablet-Based Home Monitoring in Age-Related Macular Degeneration.

PURPOSE: The aim of this study was to determine the short-term compliance with regular home monitoring of macular retinal sensitivity (RS) in intermediate age-related macular degeneration (iAMD). Home-based outcomes were compared with in-clinic outcomes determined using (1) the same tablet device under supervision, and (2) the Macular Integrity Assessment (MaIA) microperimeter. DESIGN: Single-center longitudinal compliance and reliability study. METHODS: A total of 73 participants with iAMD were trained to perform macular field testing with the Melbourne Rapid Fields-macular (MRF-m) iPad application. Volunteers were asked to return 6 weekly tests from home, guided by audio instructions. We determined compliance with weekly testing and surveyed for factors that limited compliance. Test reliability (false positive, false negative) and RS were compared to in-clinic assays (MaIA). Data are given as mean ± SD or as median [quartile 1-3 range]. Group comparisons were achieved with bootstrap to define the 95% confidence limits. RESULTS: A total of 59 participants submitted 6 home examinations with a median intertest interval of 8.0 [7.0-17] days. Compliance with weekly testing (7 days ±24 hours) was 55%. The main barrier to compliance was information technology (IT) logistic reasons. Of 694 home examinations submitted, 96% were reliable (false-positive results <25%). The mean RS returned by the tablet was significantly higher (+3.2 dB, P < .05) compared to the MaIA. CONCLUSIONS: Home monitoring produces reliable results that differ from in-clinic tests because of test design. This should not affect self-monitoring once an at-home baseline is established, but these differences will affect comparisons with in-clinic outcomes. Reasonable compliance with weekly testing was achieved. Improved IT support might lead to better compliance.

Interobserver Agreement of Electrode to Retina Distance Measurements in a Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis.

Purpose: The electrode to retina (ER) distance is an important contributory factor to the safety and efficacy of a suprachoroidal retinal prosthesis. Measuring ER distance may be performed by different observers during multisite studies. The aim of this study was to assess the interobserver agreement in measuring ER distance. Methods: Three independent, trained observers measured ER distance from the center of each suprachoroidal electrode to the inner retinal pigment epithelium in spectral-domain optical coherence tomography (SD-OCT) B-scans. A total of 121 ER distance measurements from 77 B-scans collected over 5 months from one subject implanted with a second-generation 44-channel suprachoroidal retinal prosthesis (NCT03406416) were made by each observer. Results: ER distance ranged from 208 to 509 µm. Pearson's correlation coefficient (ρ) showed agreement of 0.99 (95% confidence interval [CI] = 0.98-0.99) in measuring ER for each pairwise comparison. The mean difference in ER distance between observers ranged from 2.4 to 6.4 µm with pairwise limits of agreement (95% CI) of ±20 µm (5.5% of mean). Intraclass correlation coefficient (ICC) showed agreement of 0.98 (95% CI = 0.97-0.99) between observers. Conclusions: There is high agreement in measuring ER distances for suprachoroidal retinal prostheses using our systematic approach between multiple, trained observers, supporting the use of a single observer for each image. Translational Relevance: High interobserver agreement outcomes indicate that multiple, trained observers can be used to take ER measurements across different images in suprachoroidal retinal prosthesis studies. This improves multisite study efficiency and gives confidence in interpreting results relating to the safety and efficacy of suprachoroidal retinal prostheses.

A Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis: Long-Term Observation of the Electrode-Tissue Interface.

Purpose: To report the long-term observations of the electrode-tissue interface and perceptual stability in humans after chronic stimulation with a 44-channel suprachoroidal retinal implant. Methods: Four subjects (S1-4) with end-stage retinitis pigmentosa received the implant unilaterally (NCT03406416). Electrode impedances, electrode-retina distance (measured using optical coherence tomography imaging), and perceptual thresholds were monitored up to 181 weeks after implantation as the subjects used the prosthesis in the laboratory and in daily life. Stimulation charge density was limited to 32 µC/cm2 per phase. Results: Electrode impedances were stable longitudinally. The electrode-retina distances increased after surgery and then stabilized, and were well-described by an asymptotic exponential model. The stabilization of electrode-retina distances was variable between subjects, stabilizing after 45 weeks for S1, 63 weeks for S2, and 24 weeks for S3 (linear regression; Pgradient > 0.05). For S4, a statistically significant increase in electrode-retina distance persisted (P < 0.05), but by the study end point the rate of increase was clinically insignificant (exponential model: 0.33 µm/wk). Perceptual electrical thresholds were stable in one subject, decreased over time in two subjects (linear model; P < 0.05), and increased slightly in one subject but remained within the predefined charge limits (P = 0.02). Conclusions: Chronic stimulation with the suprachoroidal retinal prosthesis over 3 years resulted in stable impedances, small individual changes in perceptual electrical thresholds, and no clinically significant increase in electrode-retina distances after a period of settling after surgery. Translational Relevance: Chronic stimulation with the 44-channel suprachoroidal retinal implant with a charge density of up to 32 µC/cm2 per phase is suitable for long-term use in humans.

A Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis: Interim Clinical Trial Results.

Purpose: To report the initial safety and efficacy results of a second-generation (44-channel) suprachoroidal retinal prosthesis at 56 weeks after device activation. Methods: Four subjects, with advanced retinitis pigmentosa and bare-light perception only, enrolled in a phase II trial (NCT03406416). A 44-channel electrode array was implanted in a suprachoroidal pocket. Device stability, efficacy, and adverse events were investigated at 12-week intervals. Results: All four subjects were implanted successfully and there were no device-related serious adverse events. Color fundus photography indicated a mild postoperative subretinal hemorrhage in two recipients, which cleared spontaneously within 2 weeks. Optical coherence tomography confirmed device stability and position under the macula. Screen-based localization accuracy was significantly better for all subjects with device on versus device off. Two subjects were significantly better with the device on in a motion discrimination task at 7, 15, and 30°/s and in a spatial discrimination task at 0.033 cycles per degree. All subjects were more accurate with the device on than device off at walking toward a target on a modified door task, localizing and touching tabletop objects, and detecting obstacles in an obstacle avoidance task. A positive effect of the implant on subjects' daily lives was confirmed by an orientation and mobility assessor and subject self-report. Conclusions: These interim study data demonstrate that the suprachoroidal prosthesis is safe and provides significant improvements in functional vision, activities of daily living, and observer-rated quality of life. Translational Relevance: A suprachoroidal prosthesis can provide clinically useful artificial vision while maintaining a safe surgical profile.

Functional Vision in the Real-World Environment With a Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis.

Purpose: In a clinical trial (NCT03406416) of a second-generation (44-channel) suprachoroidal retinal prosthesis implanted in subjects with late-stage retinitis pigmentosa (RP), we assessed performance in real-world functional visual tasks and emotional well-being. Methods: The Functional Low-Vision Observer Rated Assessment (FLORA) and Impact of Vision Impairment-Very Low Vision (IVI-VLV) instruments were administered to four subjects before implantation and after device fitting. The FLORA contains 13 self-reported and 35 observer-reported items ranked for ease of conducting task (impossible-easy, central tendency given as mode). The IVI-VLV instrument quantified the impact of low vision on daily activities and emotional well-being. Results: Three subjects completed the FLORA for two years after device fitting; the fourth subject ceased participation in the FLORA after fitting for reasons unrelated to the device. For all subjects at each post-fitting visit, the mode ease of task with device ON was better or equal to device OFF. Ease of task improved over the first six months with device ON, then remained stable. Subjects reported improvements in mobility, functional vision, and quality of life with device ON. The IVI-VLV suggested self-assessed vision-related quality of life was not impacted by device implantation or usage. Conclusions: Subjects demonstrated sustained improved ease of task scores with device ON compared to OFF, indicating the device has a positive impact in the real-world setting. Translational Relevance: Our suprachoroidal retinal prosthesis shows potential utility in everyday life, by enabling an increased environmental awareness and improving access to sensory information for people with end-stage RP.

Oculomotor Responses to Dynamic Stimuli in a 44-Channel Suprachoroidal Retinal Prosthesis.

Purpose: To investigate oculomotor behavior in response to dynamic stimuli in retinal implant recipients. Methods: Three suprachoroidal retinal implant recipients performed a four-alternative forced-choice motion discrimination task over six sessions longitudinally. Stimuli were a single white bar ("moving bar") or a series of white bars ("moving grating") sweeping left, right, up, or down across a 42″ monitor. Performance was compared with normal video processing and scrambled video processing (randomized image-to-electrode mapping to disrupt spatiotemporal structure). Eye and head movement was monitored throughout the task. Results: Two subjects had diminished performance with scrambling, suggesting retinotopic discrimination was used in the normal condition and made smooth pursuit eye movements congruent to the moving bar stimulus direction. These two subjects also made stimulus-related eye movements resembling optokinetic reflex (OKR) for moving grating stimuli, but the movement was incongruent with stimulus direction. The third subject was less adept at the task, appeared primarily reliant on head position cues (head movements were congruent to stimulus direction), and did not exhibit retinotopic discrimination and associated eye movements. Conclusions: Our observation of smooth pursuit indicates residual functionality of cortical direction-selective circuits and implies a more naturalistic perception of motion than expected. A distorted OKR implies improper functionality of retinal direction-selective circuits, possibly due to retinal remodeling or the non-selective nature of the electrical stimulation. Translational Relevance: Retinal implant users can make naturalistic eye movements in response to moving stimuli, highlighting the potential for eye tracker feedback to improve perceptual localization and image stabilization in camera-based visual prostheses.

Secondary and Exploratory Outcomes of the Subthreshold Nanosecond Laser Intervention Randomized Trial in Age-Related Macular Degeneration: A LEAD Study Report.

PURPOSE: To evaluate the secondary and exploratory outcomes of the Laser Intervention in Early Stages of Age-Related Macular Degeneration (LEAD) study, a 36-month trial of a subthreshold nanosecond laser (SNL) treatment for slowing the progression to late age-related macular degeneration (AMD) in its early stages. DESIGN: Multicenter, randomized, sham-controlled trial. PARTICIPANTS: Two-hundred ninety-two patients with bilateral large drusen. METHODS: Participants were randomly assigned to receive SNL or sham treatment to the study eye at 6-month intervals. MAIN OUTCOME MEASURES: The secondary outcome measure of the LEAD study was the time to development of late AMD, defined by multimodal imaging in the non-study eye. The exploratory outcome measures were the rate of change in best-corrected visual acuity (BCVA), low-luminance visual acuity, microperimetric mean sensitivity, drusen volume in the study and non-study eyes, and participant-reported outcomes based on the Night Vision Questionnaire and Impact of Vision Impairment questionnaire. RESULTS: Progression to late AMD in the non-study eye was not significantly delayed with SNL treatment (hazard ratio, 0.83; 95% confidence interval, 0.40-1.71; P = 0.611). There was no evidence of effect modification based on the coexistence of reticular pseudodrusen; interaction P = 0.065). There was no significant difference between study groups in the rate of change of low-luminance visual acuity, microperimetric mean sensitivity, and drusen volume in the study or non-study eyes, and Night Vision Questionnaire and Impact of Vision Impairment questionnaire scores (all P ≥ 0.167). The rate of BCVA decline was slightly higher for participants in the SNL group compared with the sham treatment group in the study eye (-0.54 and 0.23 letters/year, respectively; P < 0.001) but not the non-study eye (-0.48 and -0.56 letters/year, respectively; P = 0.628). CONCLUSIONS: Subthreshold nanosecond laser treatment of one eye did not have an effect on delaying progression to late AMD in the fellow eye and did not, in general, have an impact on the exploratory structural, functional, and participant-reported outcomes.

Interpretation of Subretinal Fluid Using OCT in Intermediate Age-Related Macular Degeneration.

PURPOSE: To determine the natural history of asymptomatic, subretinal fluid (SRF) in intermediate age-related macular degeneration (iAMD) and highlight the entity of nonexudative detachment of the neurosensory retina (NEDNR). DESIGN: Prospective, observational case series. PARTICIPANTS: Cases of iAMD with bilateral drusen >125 µm who were participating in a longitudinal study, in whom spectral-domain (SD)-OCT imaging detected asymptomatic SRF. METHODS: Participants underwent clinical examinations every 6 months with multimodal imaging that included infrared reflectance, fundus autofluorescence, and SD-OCT. The grading center identified eyes with SRF. Eyes with SRF ≤30 µm were monitored more regularly, whereas eyes with SRF >30 µm underwent fluorescein angiography (FA) and indocyanine green angiography (ICGA). Subretinal fluid without evidence of neovascularization or polyp was termed "NEDNR". All cases of SRF underwent swept-source OCT angiography (SS-OCTA) to determine if choroidal neovascularization (CNV) was present and were then followed prospectively. MAIN OUTCOME MEASURES: Natural history of iAMD eyes with SRF that had no evidence of neovascularization during the monitoring period of 30 to 54 months. RESULTS: Sixteen eyes of 12 patients with iAMD developed asymptomatic SRF over a follow-up period of 30 to 54 months. Four eyes developed occult CNV on FA and were no longer followed in this study. Four eyes developed SRF ≤30 µm, and 8 eyes developed SRF >30 µm, with 11 of the 12 eyes developing subretinal hyperreflective material (SHRM). None of these 12 eyes showed any evidence of neovascularization at the initial detection of SRF and were termed "NEDNR". During the follow-up period of 12 to 36 months after the onset of SRF, only 1 eye developed exudative CNV. The remaining 11 eyes failed to demonstrate any abnormal choroidal vasculature on SS-OCTA, including 4 eyes with cuticular drusen in which SHRM developed into a large subfoveal vitelliform-like deposit. CONCLUSIONS: Multimodal imaging is helpful for the interpretation and management of asymptomatic SRF in iAMD. In some eyes, all imaging, including SS-OCTA, failed to demonstrate subclinical neovascularization, and we use the acronym NEDNR to describe these cases. This phenotype within iAMD needs to be recognized and monitored to determine if and when treatment might be needed.